1. Field of the Invention
The present invention relates to an improved apparatus and process for joining a tube inserted within another tube in proximity to the respective ends. More particularly, the improved apparatus and improved process of the present invention involve the compression and subsequent radial expansion of a pair of elastomeric bars positioned along the generally open sides of a bushing means. The elastomeric bars expand against the inner surface of the first tube at selective points causing selective expansion of the tube wall against the inner surface of the second tube to create a selective interference fit between the wall of the first tube and the wall of the second tube in proximity to their respective ends.
2. Description of the Prior Art
Prior art methods of expanding tubes include the use of metal rollers located inside the tube which move outwardly from a central position as the rollers are mechanically rotated about the central position. Such methods typically expand the tube only in a round shape about the entire circumference of the tube with the final shape of the tube being a concentric circle relative to the starting position of the tube. In our improved invention, longitudinal zones of expansion are used to mechanically lock the tubes together.
Other prior art such as U.S. Pat. No. 4,109,365 by Tygart involve the compression of hard rubber or polyurethane by piston forces applied from both ends of the tube, thereby making it difficult to expand the tube at greater distances from either end of the tube as when an expandable joint is made in tubular piling at the bottom of the ocean. Our invention utilizes a compression force applied from only one end of the tube thereby allowing an expansion to occur deep within the tube.
U.S. Pat. No. 4,152,821 by Scott teaches a process for joining a plastic pipe to a plastic or metal coupling by compression of a rubber plug against the inner walls of the plastic pipe. U.S. Pat. No. 4,420,866 by Mueller discloses an apparatus and process for expanding a tube selective points about its circumference to join with another tube.
We have considerably improved the invention disclosed in U.S. Pat. No. 4,420,866 which will be incorporated herein by reference. We have added a ring that threads to the outside of the outer cap in order to permit the axial position adjustment of the pair of elastomeric bars. This feature is not taught in U.S. Pat. No. 4,420,866. We have also removed the longitudinal slots including the retainers of the bushing and have opened the sides of the bushing in order to facilitate the lodging of the pair of elastomeric bars along the open sides. The bushing of the present invention with its open sides is generally figure eight in shape.